PowerShell: How to retrieve a specific property _exclusively_

This is because the -properties switch is not a formatting tool, it is intended as a way to receive more information than the default values already included.

From the Get-ADOrganizationalUnit article.

Specifies the properties of the output object to retrieve from the server. Use this parameter to retrieve properties that are not included in the default set.

If you want to format your output, you're better of sticking with the select-object statement.

You would need to use both, to specify which properties to retrieve from the DC, and which ones to select and ultimately display. -Properties * is a potential performance basher since the DSA will need to return every attribute that has a value, including certificates and other binary values you might not have need for

In a script utilizing the AD cmdlets I would use the splatting operator (@) and do the following:

$ADSplat = @{
    "SearchBase" = 'OU=Houston,DC=contoso,DC=net'
    "Filter"     = 'Name -eq "SomeOU"'
    "Properties" = "Description","Streetaddress","State","postalcode"
}
$ADOU = Get-ADOrganizationalUnit @ADSplat | Select-Object $ADSplat["Properties"]

If you do this consistently, your scripts become über-easy to update/edit, since every query is defined in the same readable hastable format

If I'm at the shell and mid-oneliner come to think about the properties I need, I'd do something like (using Get-ADUser as an example):

Get-ADUser username -Properties ($p = "manager","memberOf","cn") |select $p

Also consider using LDAP or ADSI http://blogs.technet.com/b/heyscriptingguy/archive/2010/12/01/use-powershell-to-query-active-directory-from-the-console.aspx